Add cpuid bit definition for the SUCCOR feature. This cpuid bit is required to
be exposed to guests to allow them to handle machine check exceptions on AMD
hosts.

----
v2:
  - Add "succor" feature word.
  - Add case to kvm_arch_get_supported_cpuid for the SUCCOR feature.

Reported-by: William Roche <william.roche@oracle.com>
Reviewed-by: Joao Martins <joao.m.martins@oracle.com>
Signed-off-by: John Allen <john.allen@amd.com>
---
 target/i386/cpu.c     | 18 +++++++++++++++++-
 target/i386/cpu.h     |  4 ++++
 target/i386/kvm/kvm.c |  2 ++
 3 files changed, 23 insertions(+), 1 deletion(-)

diff --git a/target/i386/cpu.c b/target/i386/cpu.c
index bca776e1fe..5fa2dde732 100644
--- a/target/i386/cpu.c
+++ b/target/i386/cpu.c
@@ -1032,6 +1032,22 @@ FeatureWordInfo feature_word_info[FEATURE_WORDS] = {
         .tcg_features = TCG_APM_FEATURES,
         .unmigratable_flags = CPUID_APM_INVTSC,
     },
+    [FEAT_8000_0007_EBX] = {
+        .type = CPUID_FEATURE_WORD,
+        .feat_names = {
+            NULL, "succor", NULL, NULL,
+            NULL, NULL, NULL, NULL,
+            NULL, NULL, NULL, NULL,
+            NULL, NULL, NULL, NULL,
+            NULL, NULL, NULL, NULL,
+            NULL, NULL, NULL, NULL,
+            NULL, NULL, NULL, NULL,
+            NULL, NULL, NULL, NULL,
+        },
+        .cpuid = { .eax = 0x80000007, .reg = R_EBX, },
+        .tcg_features = 0,
+        .unmigratable_flags = 0,
+    },
     [FEAT_8000_0008_EBX] = {
         .type = CPUID_FEATURE_WORD,
         .feat_names = {
@@ -6556,7 +6572,7 @@ void cpu_x86_cpuid(CPUX86State *env, uint32_t index, uint32_t count,
         break;
     case 0x80000007:
         *eax = 0;
-        *ebx = 0;
+        *ebx = env->features[FEAT_8000_0007_EBX];
         *ecx = 0;
         *edx = env->features[FEAT_8000_0007_EDX];
         break;
diff --git a/target/i386/cpu.h b/target/i386/cpu.h
index ddf53937b4..5dd41e3d69 100644
--- a/target/i386/cpu.h
+++ b/target/i386/cpu.h
@@ -607,6 +607,7 @@ typedef enum FeatureWord {
     FEAT_7_1_EAX,       /* CPUID[EAX=7,ECX=1].EAX */
     FEAT_8000_0001_EDX, /* CPUID[8000_0001].EDX */
     FEAT_8000_0001_ECX, /* CPUID[8000_0001].ECX */
+    FEAT_8000_0007_EBX, /* CPUID[8000_0007].EBX */
     FEAT_8000_0007_EDX, /* CPUID[8000_0007].EDX */
     FEAT_8000_0008_EBX, /* CPUID[8000_0008].EBX */
     FEAT_8000_0021_EAX, /* CPUID[8000_0021].EAX */
@@ -953,6 +954,9 @@ uint64_t x86_cpu_get_supported_feature_word(FeatureWord w,
 /* Packets which contain IP payload have LIP values */
 #define CPUID_14_0_ECX_LIP              (1U << 31)
 
+/* RAS Features */
+#define CPUID_8000_0007_EBX_SUCCOR      (1U << 1)
+
 /* CLZERO instruction */
 #define CPUID_8000_0008_EBX_CLZERO      (1U << 0)
 /* Always save/restore FP error pointers */
diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c
index 810f586a59..384b702fef 100644
--- a/target/i386/kvm/kvm.c
+++ b/target/i386/kvm/kvm.c
@@ -476,6 +476,8 @@ uint32_t kvm_arch_get_supported_cpuid(KVMState *s, uint32_t function,
          */
         cpuid_1_edx = kvm_arch_get_supported_cpuid(s, 1, 0, R_EDX);
         ret |= cpuid_1_edx & CPUID_EXT2_AMD_ALIASES;
+    } else if (function == 0x80000007 && reg == R_EBX) {
+        ret |= CPUID_8000_0007_EBX_SUCCOR;
     } else if (function == KVM_CPUID_FEATURES && reg == R_EAX) {
         /* kvm_pv_unhalt is reported by GET_SUPPORTED_CPUID, but it can't
          * be enabled without the in-kernel irqchip
-- 
2.43.0